Published: September 2014

A girl aged 8 years was referred by her pediatric dentist,
who had examined the clinical and radiographic presentation of the maxillary
permanent incisors, which had made her concerned about the possibility of
bilateral canine eruption problems. The young girl exhibited class 1 occlusal
relationships in the early mixed dentition stage with widely spaced maxillary
incisors. Deciduous canines and molars were present, in addition to all four
permanent first molars. As the result of trauma a year or so earlier, the left
central incisor had fractured off its mesial incisal corner, but the tooth was
vital with a normal response to the pulp tester.

The child arrived for her first visit with a panoramic
radiograph that had been taken in February 2012 and the relationship between
the unerupted permanent canine crowns and the lateral incisor apices could be
clearly seen.

Fig. 1a, b. The first of these two figures shows the
initial relationship between the long axes of the incisor teeth and the
unerupted canines in the maxilla in the “Ugly Duckling” stage of dental development.
At this age, the canines are high up on the roots of the incisors, restricting
the roots, which become tipped towards the midline, thereby causing spacing and
distal flaring of their crowns. The second diagram describes how eruptive
movement of the canines is guided by the distal surface of the roots and,
eventually, the crowns of the lateral incisors. This releases the incisor roots
from the restrictive influence, while pushing the crowns of the incisors
together and changing the orientation of the long axes of each of these teeth.

This figure is taken from the second edition of my textbook
entitled: Treatment of Impacted Teeth, published by Informa
Healthcare, for whose permission to publish on this website, I am grateful.

The pediatric dentist’s worries were focused on the fact
that the long axes of the maxillary incisors were oriented such that their
apices were distally displaced, which is highly unusual. In the “ugly duckling”
stage of development of the anterior dentition, the crowns of the four incisors
are typically flared distally and labially, with their long axes convergent
apically and held tightly together by the presence of the crowns of the
uneruptedcanine, high up on the distal
side of the lateral incisor roots (Fig. 1).

The roots of the lateral incisor teeth in this case were divergent as
they proceeded apically (Fig. 2). The concern was that these root apices would be
distally located to the crowns of the developing canines and would prevent
normal eruption by, thus, blocking their eruption paths.

The treatment plan was to close the incisor spacing by
mesially uprighting the roots of the four incisors towards the midline, with
the expectation that the canine crown relationship with the lateral incisor
roots would improve and permit a more favorable eruption path for the canines.
This would then improve the chances for the normal and spontaneous eruption of
the maxillary canines.

Fig. 3a. The colored locating jigs on the brackets at
the time of bonding show the degree of divergence of the longaxes of the incisor teeth.

Fig. 3b. The initial 0.014” round NiTi archwire is
ligated on 6 January 2014. N.B. Tip Edge brackets permit a broad degree of tip
in the horizontal slot, enabling full ligation before uprighting is achieved.

Accordingly, molar bands and Tip Edge Plus brackets
(TP Orthodontics Inc.) brackets were placed on all the permanent and deciduous teeth
in the maxilla, on 6 January, 2014 (Fig. 3). Leveling and alignment were
quickly achieved using a 0.014” NiTi archwire and anterior spaces closed.

Fig. 4a. The 0.020” round steel base arch is still in
place after the uprighting spring auxiliaries have bee removed, immediately
prior to de-bonding.

Fig. 4b. Following de-bonding on 7 July 2014, the
lateral incisors crowns, in particular, may be seen to be distally flared, as
seen in a naturally occurring and normally developing incisor alignment, in the
mixed dentition stage.

Mesial uprighting of the strongly divergent roots of the teeth was then performed
until the long axes of the incisor teeth were made to converge as they
proceeded apically, which is what one would expect to see in normal development
at this age (Fig. 4).This was accomplished
using a base arch of 0.020” stainless steel round and employing individual
uprighting springs in the vertical slots of the 4 incisor brackets. The
panoramic film taken immediately prior to debonding shows the re-orientation of
the long axes of the incisors and it also shows considerable improvement in
their relation to the unerupted canines, which can be seen to be moving down
the distal aspect of the lateral incisors in a new eruption path towards
spontaneous eruption into their places in the dental scheme (Fig. 5).

Fig. 5a, b. The panoramic and periapical views seen
post-treatment, show the converging long axes of the roots. The canines now
appear to be more vertically directed, on the distal of the lateral incisor
roots and heading downwards in an excellent eruption path.

At the completion of treatment, debonding was performed on
7 July 2014, a simple Hawley retainer was placed and the patient was referred
for the extraction of the maxillary deciduous canines and first deciduous
molars. This precaution was taken to further encourage the canines to erupt
into their correct place. The rationale for the extraction of the deciduous
canines is well known and has become an established interceptive measure in the
mixed dentition, when canine impaction is suspected. However, the concurrent
extraction of the deciduous first molar is a less known remedy.1 Its
extraction will serve to encourage the rapid eruption of the first premolar. When
the premolar erupts, its bulky crown will have become distanced from its close proximity
to the canine, in favor of the mesio-distally narrower cervical and bifurcation
areas. This provides space for the canine to drift distally enough, it is
hoped, for it to improve its eruption path and its chances of normal eruption.

So,
in summary for this case, 3 distinct elements were used to persuade the permanent
canines to correct their aberrant eruption paths, namely:

1.Moving the roots of the incisor
apices mesially towards the midline, to bring them mesial to the crowns of the unerupted
permanent canines

2.Extract the deciduous canines
to influence the permanent canines to redirect

3.Extract the deciduous first
molars to generate a rapid eruption of the premolars and to provide a modicum
of space distal to the canine to further encourage them to adopt a normal
eruption path.